the adrenal medulla. Although rare, they often occur as part of hereditary endocrine tumor syndromes and their study has been richly rewarding for identifying genetic events that drive tumorigenesis ( Castro-Vega et al . 2015 a ). Metastatic disease

Fernanda Vaisman, Denise P Carvalho and Mario Vaisman

( Cooper et al . 2009 ), but remain with structural disease after 6–24 months of initial therapy can have the initial risk of recurrence doubled or tripled in some cases ( Vaisman et al . 2011 ). This is especially important in patients with metastatic

, a genetic diagnosis provides an opportunity for a prophylactic thyroidectomy and cancer cure. However, most cases of MTC are sporadic, presenting with metastatic disease at diagnosis, both in the local and in the regional lymph nodes, and in distant

% ( Lloyd et al. 2017 ). Although well-differentiated GEP-NETs are often slow growing, even indolent metastatic tumors can become more aggressive and change grade over the disease course, likely due to accumulation of mutations ( Rinke et al. 2009